In the push for better resolution for HPLC (high performance liquid chromatography), the reduction of bead size has been shown to be very effective. At a given pressure, the reduction in bead size will reduce the flow rate, but increase the fluidic impedance of the separation column: for a given pressure, a 2× reduction in average bead diameter will reduce the flow rate by a factor of 4×. While high flow rates are still often desirable, low flow rates are of increasing interest, particularly in the field of proteomics, where sample injection volumes may be quite low and where LC-MS (liquid chromatography-mass spectrometry) flow rates can result in greater mass spectrometer sensitivity.
In systems where nanoflows (flows less than 1 microliter/minute) are required with high applied pressures, the fluidic path will have a high impedance to flow. Narrow channels, such as those with at least one cross-sectional dimension less than one micron (nanochannels), may be required for these very low flows, particularly if these channels are employed in flow control for the HPLC system. However, controlling channel sizes at these submicron dimensions is challenging. For isotropic etching, both channel width and depth can be difficult to control. Therefore, an improved method of fabricating nanochannels is desirable.